// 自然写互动课堂平板端应用软件 V1.0
// bloc/homework_bloc.dart - 作业状态管理（Bloc模式）

import 'dart:async';

/// 作业状态枚举
enum HomeworkStatus {
  /// 待完成
  pending,

  /// 进行中（已开始作答）
  inProgress,

  /// 已提交
  submitted,

  /// 已批改
  graded,

  /// 已过期
  expired,
}

/// 作业数据模型
class HomeworkItem {
  final String id;
  final String title;
  final String subject;
  final String teacherName;
  final HomeworkStatus status;
  final DateTime? assignedAt;
  final DateTime? deadline;
  final DateTime? submittedAt;
  final int? score;
  final int totalQuestions;
  final int answeredQuestions;
  final String? coverImageUrl;

  HomeworkItem({
    required this.id,
    required this.title,
    required this.subject,
    required this.teacherName,
    this.status = HomeworkStatus.pending,
    this.assignedAt,
    this.deadline,
    this.submittedAt,
    this.score,
    this.totalQuestions = 0,
    this.answeredQuestions = 0,
    this.coverImageUrl,
  });

  /// 是否已过截止时间
  bool get isOverdue =>
      deadline != null && DateTime.now().isAfter(deadline!);

  /// 作答进度百分比
  double get progress => totalQuestions > 0
      ? answeredQuestions / totalQuestions
      : 0.0;

  /// 从JSON解析
  factory HomeworkItem.fromJson(Map<String, dynamic> json) {
    return HomeworkItem(
      id: json['id'] ?? '',
      title: json['title'] ?? '',
      subject: json['subject'] ?? '',
      teacherName: json['teacher_name'] ?? '',
      status: _parseStatus(json['status']),
      assignedAt: json['assigned_at'] != null
          ? DateTime.tryParse(json['assigned_at'])
          : null,
      deadline: json['deadline'] != null
          ? DateTime.tryParse(json['deadline'])
          : null,
      submittedAt: json['submitted_at'] != null
          ? DateTime.tryParse(json['submitted_at'])
          : null,
      score: json['score'],
      totalQuestions: json['total_questions'] ?? 0,
      answeredQuestions: json['answered_questions'] ?? 0,
      coverImageUrl: json['cover_image_url'],
    );
  }

  /// 解析状态字符串
  static HomeworkStatus _parseStatus(String? status) {
    switch (status) {
      case 'pending':
        return HomeworkStatus.pending;
      case 'in_progress':
        return HomeworkStatus.inProgress;
      case 'submitted':
        return HomeworkStatus.submitted;
      case 'graded':
        return HomeworkStatus.graded;
      case 'expired':
        return HomeworkStatus.expired;
      default:
        return HomeworkStatus.pending;
    }
  }
}

/// 作业详情中的题目数据
class HomeworkQuestion {
  final String id;
  final int index;
  final String type;
  final String content;
  final String? imageUrl;
  final List<String>? options;
  final String? correctAnswer;
  final String? studentAnswer;
  final List<Map<String, dynamic>>? studentStrokes;
  final int? questionScore;
  final int? earnedScore;
  final String? teacherComment;

  HomeworkQuestion({
    required this.id,
    required this.index,
    required this.type,
    required this.content,
    this.imageUrl,
    this.options,
    this.correctAnswer,
    this.studentAnswer,
    this.studentStrokes,
    this.questionScore,
    this.earnedScore,
    this.teacherComment,
  });

  /// 从JSON解析
  factory HomeworkQuestion.fromJson(Map<String, dynamic> json) {
    return HomeworkQuestion(
      id: json['id'] ?? '',
      index: json['index'] ?? 0,
      type: json['type'] ?? 'write',
      content: json['content'] ?? '',
      imageUrl: json['image_url'],
      options: json['options'] != null
          ? List<String>.from(json['options'])
          : null,
      correctAnswer: json['correct_answer'],
      studentAnswer: json['student_answer'],
      studentStrokes: json['student_strokes'] != null
          ? List<Map<String, dynamic>>.from(json['student_strokes'])
          : null,
      questionScore: json['question_score'],
      earnedScore: json['earned_score'],
      teacherComment: json['teacher_comment'],
    );
  }
}

// ============================================================
//  Bloc Events（作业相关事件定义）
// ============================================================

/// 作业事件基类
abstract class HomeworkEvent {}

/// 加载作业列表事件
class LoadHomeworkListEvent extends HomeworkEvent {
  final HomeworkStatus? filterStatus;
  final int page;
  final bool refresh;

  LoadHomeworkListEvent({
    this.filterStatus,
    this.page = 1,
    this.refresh = false,
  });
}

/// 下载作业详情事件（用于离线作答）
class DownloadHomeworkEvent extends HomeworkEvent {
  final String homeworkId;
  DownloadHomeworkEvent(this.homeworkId);
}

/// 保存作答进度事件（本地暂存）
class SaveAnswerProgressEvent extends HomeworkEvent {
  final String homeworkId;
  final String questionId;
  final String? textAnswer;
  final List<Map<String, dynamic>>? strokeData;

  SaveAnswerProgressEvent({
    required this.homeworkId,
    required this.questionId,
    this.textAnswer,
    this.strokeData,
  });
}

/// 提交作业事件
class SubmitHomeworkEvent extends HomeworkEvent {
  final String homeworkId;
  SubmitHomeworkEvent(this.homeworkId);
}

/// 查看批改结果事件
class ViewGradeResultEvent extends HomeworkEvent {
  final String homeworkId;
  ViewGradeResultEvent(this.homeworkId);
}

// ============================================================
//  Bloc States（作业相关状态定义）
// ============================================================

/// 作业状态基类
abstract class HomeworkState {}

/// 初始状态
class HomeworkInitialState extends HomeworkState {}

/// 加载中状态
class HomeworkLoadingState extends HomeworkState {
  final String? message;
  HomeworkLoadingState({this.message});
}

/// 作业列表加载成功状态
class HomeworkListLoadedState extends HomeworkState {
  final List<HomeworkItem> homeworks;
  final bool hasMore;
  final int currentPage;
  final HomeworkStatus? currentFilter;

  /// 各状态的作业计数统计
  final Map<HomeworkStatus, int> statusCounts;

  HomeworkListLoadedState({
    required this.homeworks,
    this.hasMore = false,
    this.currentPage = 1,
    this.currentFilter,
    this.statusCounts = const {},
  });
}

/// 作业详情加载成功状态
class HomeworkDetailLoadedState extends HomeworkState {
  final HomeworkItem homework;
  final List<HomeworkQuestion> questions;
  final bool isOfflineAvailable;

  HomeworkDetailLoadedState({
    required this.homework,
    required this.questions,
    this.isOfflineAvailable = false,
  });
}

/// 作答进度保存成功状态
class AnswerSavedState extends HomeworkState {
  final String homeworkId;
  final String questionId;
  final int answeredCount;
  final int totalCount;

  AnswerSavedState({
    required this.homeworkId,
    required this.questionId,
    required this.answeredCount,
    required this.totalCount,
  });
}

/// 作业提交成功状态
class HomeworkSubmittedState extends HomeworkState {
  final String homeworkId;
  final DateTime submittedAt;

  HomeworkSubmittedState({
    required this.homeworkId,
    required this.submittedAt,
  });
}

/// 批改结果状态
class GradeResultState extends HomeworkState {
  final HomeworkItem homework;
  final List<HomeworkQuestion> questions;
  final int totalScore;
  final int earnedScore;
  final String? overallComment;

  GradeResultState({
    required this.homework,
    required this.questions,
    required this.totalScore,
    required this.earnedScore,
    this.overallComment,
  });
}

/// 错误状态
class HomeworkErrorState extends HomeworkState {
  final String message;
  final String? actionType;

  HomeworkErrorState({
    required this.message,
    this.actionType,
  });
}

// ============================================================
//  HomeworkBloc 实现
// ============================================================

/// 作业状态管理Bloc
/// 管理作业列表加载、下载、作答、提交、查看批改结果等完整流程
class HomeworkBloc {
  /// 当前状态
  HomeworkState _state = HomeworkInitialState();

  /// 状态流控制器
  final StreamController<HomeworkState> _stateController =
      StreamController<HomeworkState>.broadcast();

  /// 本地缓存的作业列表
  List<HomeworkItem> _cachedHomeworks = [];

  /// 本地缓存的作答进度 {homeworkId: {questionId: answerData}}
  final Map<String, Map<String, dynamic>> _answerCache = {};

  /// 获取当前状态
  HomeworkState get state => _state;

  /// 状态流
  Stream<HomeworkState> get stateStream => _stateController.stream;

  /// 发射新状态
  void _emit(HomeworkState newState) {
    _state = newState;
    _stateController.add(newState);
  }

  /// 处理事件分发
  void add(HomeworkEvent event) {
    if (event is LoadHomeworkListEvent) {
      _handleLoadList(event);
    } else if (event is DownloadHomeworkEvent) {
      _handleDownload(event);
    } else if (event is SaveAnswerProgressEvent) {
      _handleSaveAnswer(event);
    } else if (event is SubmitHomeworkEvent) {
      _handleSubmit(event);
    } else if (event is ViewGradeResultEvent) {
      _handleViewGrade(event);
    }
  }

  /// 处理加载作业列表
  Future<void> _handleLoadList(LoadHomeworkListEvent event) async {
    try {
      _emit(HomeworkLoadingState(message: '正在加载作业列表...'));

      // 调用API获取作业列表
      // final response = await PadApiService.instance.getHomeworkList(
      //   page: event.page,
      //   status: event.filterStatus?.name,
      // );

      // 模拟数据处理逻辑
      if (event.refresh) {
        _cachedHomeworks.clear();
      }

      // 统计各状态作业数量
      final statusCounts = <HomeworkStatus, int>{};
      for (final hw in _cachedHomeworks) {
        statusCounts[hw.status] = (statusCounts[hw.status] ?? 0) + 1;
      }

      // 根据筛选条件过滤
      List<HomeworkItem> filtered = _cachedHomeworks;
      if (event.filterStatus != null) {
        filtered = _cachedHomeworks
            .where((hw) => hw.status == event.filterStatus)
            .toList();
      }

      _emit(HomeworkListLoadedState(
        homeworks: filtered,
        hasMore: false,
        currentPage: event.page,
        currentFilter: event.filterStatus,
        statusCounts: statusCounts,
      ));
    } catch (e) {
      _emit(HomeworkErrorState(
        message: '加载作业列表失败: $e',
        actionType: 'load_list',
      ));
    }
  }

  /// 处理下载作业详情（支持离线作答）
  Future<void> _handleDownload(DownloadHomeworkEvent event) async {
    try {
      _emit(HomeworkLoadingState(message: '正在下载作业内容...'));

      // 调用API下载作业详情
      // final response = await PadApiService.instance.downloadHomework(
      //   event.homeworkId,
      // );

      // 将作业内容缓存到本地SQLite（支持离线作答）
      // await LocalRepository.instance.cacheHomework(...)

      // _emit(HomeworkDetailLoadedState(...));
    } catch (e) {
      _emit(HomeworkErrorState(
        message: '下载作业失败: $e',
        actionType: 'download',
      ));
    }
  }

  /// 处理保存作答进度（本地暂存，支持断点续答）
  Future<void> _handleSaveAnswer(SaveAnswerProgressEvent event) async {
    try {
      // 更新内存缓存
      _answerCache.putIfAbsent(event.homeworkId, () => {});
      _answerCache[event.homeworkId]![event.questionId] = {
        'text_answer': event.textAnswer,
        'stroke_data': event.strokeData,
        'saved_at': DateTime.now().toIso8601String(),
      };

      // 持久化到本地数据库
      // await LocalRepository.instance.saveAnswerProgress(...)

      // 计算已作答题目数
      final answeredCount = _answerCache[event.homeworkId]?.length ?? 0;

      _emit(AnswerSavedState(
        homeworkId: event.homeworkId,
        questionId: event.questionId,
        answeredCount: answeredCount,
        totalCount: 0, // 从缓存的作业详情中获取
      ));
    } catch (e) {
      _emit(HomeworkErrorState(
        message: '保存作答进度失败: $e',
        actionType: 'save_answer',
      ));
    }
  }

  /// 处理提交作业
  Future<void> _handleSubmit(SubmitHomeworkEvent event) async {
    try {
      _emit(HomeworkLoadingState(message: '正在提交作业...'));

      // 收集所有作答数据
      final answers = _answerCache[event.homeworkId] ?? {};

      // 构建提交数据（含笔迹页面数据）
      final strokePages = answers.entries.map((entry) {
        return {
          'question_id': entry.key,
          'answer': entry.value,
        };
      }).toList();

      // 调用API提交
      // final response = await PadApiService.instance.submitHomework(
      //   homeworkId: event.homeworkId,
      //   strokePages: strokePages,
      // );

      // 提交成功后清除本地缓存
      _answerCache.remove(event.homeworkId);

      _emit(HomeworkSubmittedState(
        homeworkId: event.homeworkId,
        submittedAt: DateTime.now(),
      ));
    } catch (e) {
      _emit(HomeworkErrorState(
        message: '提交作业失败: $e',
        actionType: 'submit',
      ));
    }
  }

  /// 处理查看批改结果
  Future<void> _handleViewGrade(ViewGradeResultEvent event) async {
    try {
      _emit(HomeworkLoadingState(message: '正在加载批改结果...'));

      // 调用API获取批改结果
      // final response = await PadApiService.instance.getHomeworkResult(
      //   event.homeworkId,
      // );

      // _emit(GradeResultState(...));
    } catch (e) {
      _emit(HomeworkErrorState(
        message: '加载批改结果失败: $e',
        actionType: 'view_grade',
      ));
    }
  }

  /// 释放资源
  void dispose() {
    _stateController.close();
    _cachedHomeworks.clear();
    _answerCache.clear();
  }
}